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1129 fps, exact reason?

Discussion in 'Handloading and Reloading' started by Alabama2010, Mar 27, 2010.

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  1. Alabama2010

    Alabama2010 Member

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    I've been reading about F-class and Palma matches and think this is something I'd like to try starting later this year, so I've been reading up on long distance target shooting. Every source I've read talks about the bullet velocity needing to be 1129 fps at 100yds (or thereabout depending on elevation). They give the BC and MV needed to achieve that as well. But they never mention why it needs to be supersonic at 1000 yds. The only thing that comes to mind is that it must be at this velocity that the bullet begins to tumble or drop precipitously. Anyone know for sure? Is that correct? I'm sure a BTHP would still kill medium sized game if traveling at 1000 fps vs. 1129 fps- so it can't be that....
    Thanks.
     
  2. Ridgerunner665

    Ridgerunner665 Member

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    1129 fps is the average speed of sound at sea level...

    Stability...thats the answer you're looking for (in a nutshell)
     
  3. rcmodel

    rcmodel Member in memoriam

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    Ever watch those old movies where John Glenn was trying to break the sound barrier in a Bell X-1 rocket plane?
    Remember the airplane buffeting and instability he experienced as he broke the speed of sound the first time?

    If the bullet slows below the speed of sound at 900 or 950 yards, the supersonic bow shock wave goes away and forces the bullet to plow on through the air of it's own accord.
    It then gets buffeted during the transition from supersonic to subsonic, and may end up slightly off course by the time it gets to the 1,000 yard target.

    rc
     
  4. ReloaderFred

    ReloaderFred Member

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    Sorry RC, but it was Chuck Yeager who first broke the sound barrier on Oct. 14th, 1947.

    John Glenn was the first American to orbit the earth.

    Fred
     
  5. rcmodel

    rcmodel Member in memoriam

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    :banghead:
    Dang! I knew that!

    I'm losing it for sure!!

    rc
     
  6. SharpsDressedMan

    SharpsDressedMan member

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    I can tell you that even bullets that yaw at the 1000 yard line can be darn accurate. The big black "dot" at 1000 yards is, I believe, about 36" in diameter, and includes the 10, 9, and 8 rings. (Anyone, correct me if my info is wrong on this, I trying to recall from a couple years ago in the pits.) Many master shots used .308's, and their bullets were yawing due to crossing the sound barrier. Still in the black, and many were 9's and 10's.
     
  7. ants

    ants Member

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    These guys above know their stuff better than I do, but I believe...

    Induced yaw doesn't cause the bullet to spontaneously change course (although turbulance can do that when transitioning into or out of supersonic velocity), yaw does decelerate the projectile rapidly which strings it downward on the target and makes it more susceptible to wind drift because it loses its gyroscopic stability.

    I bet those master shooters mentioned by Sharps were very skilled at doping everything, not just wind and mirage but also yaw and pitch. It must have been fun to sit and watch them, Sharps.
     
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